Fluorescent lamps have a significant advantage over incandescent bulbs due to the ability of fluorescent lamps to produce equivalent illumination while consuming substantially less electrical power, thereby rendering fluorescent lamps more energy efficient than incandescent bulbs. However, many existing buildings have ceiling mounted recessed fixtures for incandescent lighting installed on the premises instead of recessed fluorescent lighting fixtures. Therefore, there exists a need to adapt fluorescent lamps to fit into and operate in already existing recessed incandescent lighting fixtures.
Unfortunately, the electrical requirements of fluorescent lighting adapter fixtures for installation in recessed incandescent fixtures makes them quite large in size, and therefore they often fail to satisfy spacial and aesthetic requirements. Efforts have been made to develop an assembly which meets the spacial and aesthetic design considerations of an adapter fixture for recessed incandescent lighting assemblies.
Those devices which do succeed in meeting the spacial design constraints for recessed lighting fixtures often fail to maintain long-term power requirements.
For example, one prior art device provides a configuration where a toroidal ballast surrounds the lamp in an attempt to meet both power and design considerations as described in U.S. Pat. No. 4,623,823. While this device allows all of the components to fit comfortably within a recessed lighting fixture, since the stem of the fluorescent lamp is encompassed by the toroidal ballast, the heat from the fluorescent lamp is retained instead of being dispersed. Therefore, the lamp often reaches temperatures high enough to cause its failure over periods far shorter than its rated life. Furthermore, the excessive temperatures cause early deterioration not only of the lamp and its starter, but also of the ballast components, thereby severely limiting the service life of the device as well as of the lamps.
A second prior art device as described in U.S. Pat. No. 4,746,840, while solving some of the above listed problems, added new problems. There, a rectangular core form ballast is fitted within a hollow annular housing and surrounds the lamp base. However, while this device does not subject the lamp and ballast to as much heat, it also has a more limited service life than desired due to gaps in the ballast which enlarge over time in the course of normal use. This gap widening is particularly problematic because the larger the gap widens, the more power the ballast needs in order to operate the lamp at the same level of illumination. In addition to loss of power, these gaps also result in considerable audible noise caused by the resonant vibrations of the separate ballast parts in the air gap and against one another.
Accordingly, there is a need to avoid close contact between the ballast and the light source to avoid excess heat build up, while still meeting the voltage requirements for a compact fluorescent lamp. There is also a need to minimize growth in the width of air gaps formed in the ballast in order to minimize power loss and audible noise caused by such gaps.